Suction Cutoff Unloader Valve For Compressor Capacity Control

ABSTRACT

A reciprocating compressor includes a first cylinder and a second cylinder, first and second suction cutoff unloader valve assemblies, and a controller. The first and second suction cutoff unloader valve assemblies are integral to the compressor and are capable of a rapid cycling to interrupt flow of refrigerant to the first and second cylinders. The controller operates at least one of the first suction cutoff unloader valve assembly or second suction cut-off unloader valve assembly in the rapid cycling and monitor a number of rapid cycles. In another aspect, a multi-stage compressor comprises a lower pressure stage and a higher pressure stage, and at least one suction cutoff unloader valve assembly capable of a rapid cycling to interrupt flow of refrigerant to a lower stage cylinder.

BACKGROUND

Refrigeration and air conditioning systems are commonly configured with means for system capacity control, thereby allowing the systems to improve temperature control accuracy, reliability, and energy efficiency.

Currently the most common means of refrigeration and air conditioning system capacity control is accomplished by unit cycling (turning the compressor on and off in response to fluctuations in temperature or system pressure). However, unit cycling does not allow for tight temperature control, and therefore, commonly creates discomfort and/or undesired temperature variations in the conditioned/refrigerated space.

A suction modulation valve located on a suction line downstream of the compressor is another means commonly utilized for system capacity control. However, suction modulation valves are expensive and are inefficient for system capacity control.

To overcome this, suction cutoff unloader valves integral to the compressor have been developed. One such suction cutoff unloader valve is disclosed in United States Patent Application Publication Number 2006/0218959 to Sandkoetter. Unfortunately, the suction cutoff unloader valve disclosed in Sandkoetter is adapted to be operable only in a single stage compressor, where compression is accomplished only by lower stage cylinders operating in parallel. Also, Sandkoetter discloses that all cylinder units 44 have the same switching intervals in a lower part-load range and that all the suction cutoff unloader valves are preferably operated with the same switching intervals in an upper part-load range to avoid balancing problems with the compressor pistons. By operating all the valves with the same switching intervals in either the lower or upper part-load range can greatly reduce the service life of the suction cutoff unloader valves as each valve must be opened and closed even when a reduced compressor capacity could be achieved by operating only a single valve. In the Sandkoetter application, there is also no counting or monitoring of the number of the cycles for any of the valves. Thus, it would be impossible to distribute the cycling duty between the valves.

SUMMARY

A reciprocating compressor includes a first cylinder and a second cylinder, first and second suction cutoff unloader valve assemblies, and a controller. The first and second suction cutoff unloader valve assemblies are integral to the compressor and are capable of rapid cycling to interrupt flow of refrigerant to the first and second cylinders. The controller is configured to operate at least one of the first suction cutoff unloader valve assembly and second suction cutoff unloader valve assembly in the rapid cycling and to monitor a number of rapid cycles for at least one suction cutoff unloader valve. In another aspect, a multi-stage compressor, with at least one stage being a low pressure stage and at least one other stage being a high pressure stage, has at least one suction cutoff unloader valve assembly capable of rapid cycling to interrupt flow of refrigerant to a lower stage cylinder or cylinders. The multi-stage compressor has a controller configured to operate the at least one suction cutoff unloader valve assembly on the lower stage in the rapid cycling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of one embodiment of a reciprocating compressor with high and low compression stages and with a controller electrically connected to suction cutoff unloader valve assemblies.

FIG. 1B is a cross-sectional view of another embodiment of a reciprocating compressor with the controller electrically connected to the suction cutoff unloader valve assemblies.

FIG. 2A is a partial sectional view of the suction cutoff unloader valve assembly, a cylinder head, and a cylinder block of the compressor of FIG. 1A or FIG. 1B with the suction cutoff unloader valve assembly in a fully loaded position.

FIG. 2B is a partial sectional view of the cylinder block, cylinder head, and suction cutoff unloader valve assembly of the compressor of FIG. 1A or FIG. 1B with the suction cutoff unloader valve assembly in a fully unloaded position.

FIG. 3A is a partial sectional view of a portion of the suction cutoff unloader valve assembly and cylinder head in the fully loaded position of FIG. 2A.

FIG. 3B is a partial sectional view of a portion of the suction cutoff unloader valve assembly and cylinder head in the fully unloaded position of FIG. 2B.

DETAILED DESCRIPTION

FIG. 1A shows a cross-section of a multi-stage reciprocating compressor 10M with a controller 12 is electrically connected to suction cutoff unloader valve assembly(s) 14. In the multi-stage compressor, the compression is accomplished in two steps, where the first stage of compression (from the suction pressure to intermediate pressure) is accomplished by the lower stage cylinder(s) and the second stage of compression (from the intermediate pressure to discharge pressure) is accomplished by higher stage cylinder(s). In addition to the suction cutoff unloader valve assemblies 14, the compressor 10 includes lower stage cylinder heads 16L, a higher stage cylinder head 16H, a housing 18, a cylinder block 20, lower stage cylinder banks 22L, a higher stage cylinder bank 22H, lower stage cylinders 24L, a higher stage cylinder 24H, pistons 26, connecting rods 28, a crankshaft 30, an oil sump 32, a suction manifold 34, and an intermediate manifold 36. Each of the lower and higher stage cylinder heads 16L and 16H includes a suction plenum 38 and a plenum 40.

The multi-stage reciprocating compressor 10M has suction cutoff unloader valve assembly or assemblies 14 which interconnect with the low stage cylinder heads 16L. At least one suction cut off assembly 14 is capable of operating in a rapid cycle mode. It should noted that the multi-stage compressor 10M can have one suction cutoff assembly 14 and this one assembly 14 can be capable of operating in the rapid cycle mode. In embodiments such as the one illustrated in FIG. 1A, the compressor 10M can have two or more suction cutoff unloader valve assemblies 14, where both suction cutoff valve assemblies are operating in rapid cycle mode, or only one suction cut off assembly 14 is operating in rapid cycle mode. The suction cutoff unloader valve assemblies 14 are integral to the compressor 10M. The housing 18 of the multi-stage compressor 10M has an upper portion of which forms the cylinder block 20. The cylinder block 20 forms one or more low lower stage cylinder banks 22L, as well as the higher stage cylinder bank 22H. The cylinder block 20 defines lower stage cylinders 24L and a higher stage cylinder 24H. The cylinders 24L and 24H, which extend through the cylinder block 20, are disposed adjacent to the cylinder heads 16L and 16H and the suction cutoff unloader valve assemblies 14. The lower stage cylinder heads 16L are secured to the cylinder block 20 overlaying the lower stage cylinders 24L in the low stage cylinder banks 22L. Similarly, the higher stage cylinder head 16H is secured to the cylinder block 20 overlaying the higher stage cylinders 24H in the higher stage cylinder bank 22H. Each cylinder bank 22L or 22H includes at least one cylinder 24L or 24H and may include multiple cylinders 24L or 24H which are overlaid by cylinder head 16L or 16H.

The pistons 26 are disposed in the lower and higher stage cylinders 24L and 24H and are reciprocally movable therein. The pistons 26 interconnect with the connecting rods 28 which extend internally within the multi-stage compressor 10M to interconnect with an eccentric portion of the crankshaft 30. The crankshaft 30 is rotatably disposed internally in the compressor 10M and extends through the oil sump 32. The suction manifold 34 and intermediate manifold 36 are defined by the cylinder block 20. The suction manifold 34 communicates with the oil sump 32 or directly with a suction line (not shown). The suction manifold 34 extends to the lower stage cylinder heads 16L to fluidly communicate with the suction plenum 38 in each cylinder head 16L.

In one embodiment, when the compressor 10M is in a fully loaded mode of operation, i.e. all the suction cutoff unloader valve assemblies 14 are constantly off and, are therefore, not cycling in a pulse width modulated manner, a low pressure refrigerant enters the multi-stage compressor 10M from the suction line (not shown) through an inlet port (not shown). Reviewing the operation of a single cylinder bank 22L, the reciprocating movement of the piston(s) 26 within the low stage cylinder(s) 24L draws the refrigerant from the suction line (not shown). The refrigerant is drawn into the suction manifold 34, and from there the refrigerant is drawn into the suction plenum 38 in the lower stage cylinder head 16L. From the suction plenum 38 the refrigerant passes into the low stage cylinder 24L (or cylinders) where it is compressed by the piston(s) 26. A reed valve (not shown) is positioned above each lower stage cylinder 24L to control the flow of refrigerant thereto. After leaving the lower stage cylinder 24L (or cylinders) the higher pressure vapor refrigerant is discharged through another reed valve (not shown) into the plenum 40. In the fully loaded mode, a first portion of the suction cutoff unloader valve 14 fluidly communicates with the plenum 40 and is configured to allow the refrigerant (at intermediate discharge pressure) to hold open a piston portion of the suction cutoff unloader valve 14 to permit the flow of the refrigerant through the suction plenum 38 to the lower stage cylinder(s) 24L. From the plenum 40 of the lower stage cylinder heads 16L the intermediate pressure refrigerant eventually passes to the intermediate manifold 36. The intermediate pressure refrigerant is drawn from the intermediate manifold 36 to the suction plenum 38 of the higher stage cylinder head 16H where compression of the refrigerant in the higher stage cylinder 24H (or cylinders) is repeated. However, no suction cutoff unloader valve 14 is necessary on the higher stage cylinder head 16H. It should be understood that the number of suction cutoff unloader valve assemblies can be equal to one or can be multiple assemblies. The number of lower stage cylinders can also be equal to one, but it can also can be multiple cylinders. One unloader valve assembly can also control the flow to one or multiple cylinders.

When the multi-stage reciprocating compressor 10M is in a fully unloaded mode, i.e. all the suction cutoff unloader valve assemblies 14 are constantly on and, are therefore, not cycling in a pulse width modulated manner. In this case, the first portion of each of the suction cutoff unloader valve assemblies 14 is disposed to block flow of the refrigerant from the plenum 40 to the piston portion of the suction cutoff unloader valve assembly 14. This configuration allows the biased piston portion of the suction cutoff unloader valve assembly 14 to move to a position where it substantially halts the flow of the refrigerant through the suction plenum 38 to the lower stage cylinder(s) 24L.

As will be discussed in greater detail subsequently, the controller 12 can be provided with control logic which allows one or more of the suction cutoff unloader valve assemblies 14 on the first stage of the multi-stage compressor 10M to be operated in rapid cycling (for example, using a pulse width modulation technique) to provide a continuously variable amount of capacity (part-load operation) between the capacity achieved by the multi-stage compressor 10M when the suction cutoff unloader valve assemblies 14 are in the fully unloaded position, and the capacity achieved by the multi-stage compressor 10M when the suction cutoff unloader valve assemblies 14 are in the fully loaded position. In one arrangement the low pressure stage can have of only one suction cutoff valve assembly and only one cylinder, where the suction cutoff valve is capable of operating in a rapid cycle mode. If the first stage is provided with multiple suction cutoff valves, then the controller 12 can also be provided with control logic which allows a first suction cutoff unloader valve assembly 14 and a second suction cutoff unloader valve assembly 14 to alternate rapid cycling in a mode that allows one of the suction cutoff unloader valve assemblies 14 to operate in rapid cycling while the other suction cutoff unloader valve assembly 14 is not operated in rapid cycling but is disposed in the fully loaded position or the fully unloaded position. For example, the first suction cutoff unloader valve assembly 14 can operate in rapid cycling for a first time period. During the first time period, the second suction cutoff unloader valve assembly 14 is not operated in rapid cycling. At the end of the first time period the second suction cutoff unloader valve assembly 14 is then operated in rapid cycling for a second time period. During that second time period, the first suction cutoff unloader valve assembly 14 is not operated in rapid cycling. In this manner, the suction cutoff unloader valve assemblies 14 can be alternated in rapid cycling to achieve continuously variable part-load system capacity.

If the lower stage is equipped with only one suction cutoff valve, then this valve can be operated in a rapid cycle mode. If there is more than one suction cut off valve installed on the lower stage, then the pattern of changing the suction cutoff unloader valve assembly 14 that is operated in rapid cycling while the other valve or valves, if present, are not operated in rapid cycling can be repeated for each valve in the compressor 10M. The alternating sequence can be modified, for example, instead of a single suction cutoff unloader valve assembly 14 that is operated in rapid cycling, multiple suction cutoff unloader valve assemblies 14 can be operated in rapid cycling while a single (or multiple) suction cutoff unloader valve assembly 14 is not operated in rapid cycling. In yet another embodiment, all the suction cutoff unloader valve assemblies 14 in the compressor 10M can be operated in rapid cycling to achieve part-load system capacities.

In one embodiment, one or more suction cutoff unloader valve assemblies 14 can achieve part-load system operation by rapid cycling between the fully loaded position and the fully unloaded position with a single cycle period that is between 0.3 second and 180 seconds. This cycle period is short enough to account for the inertia of the reaction of the refrigeration or air conditioning system. The operation of the suction cutoff unloader valve assemblies during the cycle period may vary. For example, within 180 second period, one suction cutoff unloader valve assembly 14 can be operated at the fully loaded position (or nearly fully loaded position) for 10 seconds and then operated at the fully unloaded (or nearly fully unloaded position) position for 170 seconds. Alternatively, the suction cutoff unloader valve assembly 14 can be operated at the fully unloaded position for 20 seconds and then operated at the fully loaded position for 160 seconds. Thus, various different operation patterns during a single cycle period are possible. In yet another example, the suction cutoff unloader valve assembly 14 operates with a 5 second cycle period. In this embodiment, the suction cutoff unloader valve assembly 14 can be operated at the fully loaded position for 1 second and then operated at the fully unloaded position for 4 seconds. Alternatively, the suction cutoff unloader valve assembly 14 can be operated at the fully unloaded position for 2 seconds and then operated at the fully loaded position for 3 seconds, etc. As illustrated with these examples, various patterns of suction cutoff unloader valve assembly operation resulting in different levels of unloading of the compressor can be achieved, even when identical cycle periods are utilized by the suction cutoff unloader valve assembly. Due to the rapid pulse width modulation of one or more of the valves, only small temperature fluctuations occur in the evaporator (not shown). These temperature fluctuations do not impair precise temperature control of the conditioned space.

As compared to FIG. 1A, which shows a compressor 10M that has lower and higher compression stages, in FIG. 1B, a compressor 10S has at least two suction cutoff valve assemblies 14 that are capable of operation in rapid cycle mode. This embodiment monitors the number of cycles for the at least two suction cutoff valve assemblies 14. By monitoring the number of cycles for the at least two suction cutoff valve assemblies 14 the controller 12 can adjust the amount of rapid cycles each valve undergoes. Thus the rapid cycling can be split between the valves to increase the longevity of the at least two suction cutoff valve assemblies 14.

FIG. 1B shows a cross-section of a single low stage compression reciprocating compressor 10S with a controller 12 electrically connected to multiple suction cutoff unloader valve assemblies 14. It should be understood that the single low stage compressor can have more than one low stage compression stages connected in parallel to each other in other embodiments. In addition to the suction cutoff unloader valve assemblies 14, the compressor 10 includes cylinder heads 16L, the housing 18, the cylinder block 20, cylinder banks 22L, cylinders 24L, pistons 26, connecting rods 28, the crankshaft 30, the oil sump 32, and the suction manifold 34. Each of the cylinder heads 16L includes the suction plenum 38 and the plenum 40. The compressor 10S includes a discharge manifold 42.

More particularly, the single stage reciprocating compressor 10S has suction cutoff unloader valve assemblies 14 which interconnect with the cylinder heads 16L. The housing 18 of the compressor 10S has an upper portion of which forms the cylinder block 20. The cylinder block 20 forms one or more cylinder banks 22L. The cylinder block 20 defines cylinders 24L. The cylinders 24L, which extend through the cylinder block 20, are disposed adjacent to the cylinder heads 16L. The cylinder heads 16L are secured to the cylinder block 20 overlaying the cylinders 24L in the cylinder banks 22L. Each cylinder bank 22L includes at least one cylinder 24L and may include multiple cylinders 24L which are overlaid by cylinder head 16L.

The pistons 26 are disposed in the cylinders 24L and are reciprocally movable therein. The pistons 26 interconnect with the connecting rods 28 which extend internally within the single stage compressor 10S to interconnect with an eccentric portion of the crankshaft 30. The crankshaft 30 is rotatably disposed internally in the compressor 10S and extends through the oil sump 32, which is optional but illustrated in the embodiment shown in FIG. 1B. The suction manifold 34 and discharge manifold 42 are defined by the cylinder block 20. Each of the cylinder heads 16L has a suction plenum 38 and plenum 40 therein which selectively communicate with the underlying cylinders 24L during a portion of the stroke of the pistons 26.

The suction manifold 34 communicates with the oil sump 32 or directly with a suction line (not shown). The suction manifold 34 extends to the cylinder heads 16L to fluidly communicate with the suction plenum 38 in each cylinder head 16L. The discharge manifold 42 selectively fluidly communicates with the plenum 40 through ports in the valve plate. The discharge manifold 42 also fluidly communicates a discharge line (not shown) to allow refrigerant discharged from the cylinders 24L to pass to the other components of the heating or cooling system.

The suction cutoff unloader valve assemblies 14 of the compressor 10S are capable of operating in a manner similar to that of the suction cutoff unloader valve assemblies 14 of the multi-stage compressor 10M shown in FIG. 1A. Thus, when the compressor 10S is in a fully loaded mode of operation, i.e. all the suction cutoff unloader valve assemblies 14 are activated but are not cycling in a pulse width modulated mode. Reviewing the operation of a single cylinder bank 22L, refrigerant is drawn through the suction manifold 34, and from there into the suction plenum 38 in the cylinder head 16L. From the suction plenum 38 the refrigerant passes into the cylinder 24L (or cylinders) where it is compressed by the piston(s) 26. After leaving the cylinder 24L (or cylinders) the higher pressure vapor refrigerant enters the plenum 40. In the fully loaded mode, a first portion of the suction cutoff unloader valve 14 fluidly communicates with the plenum 40 and is positioned to allow the refrigerant (at discharge pressure) to force open a piston portion of the suction cutoff unloader valve 14 to permit the flow of the refrigerant through the suction plenum 38 to the cylinder 24L. From the plenum 40 of the cylinder head 16L the refrigerant passes to the discharge manifold 42. From the discharge manifold 42 the compressed refrigerant exits the compressor 10S through an outlet port (not shown) to other components of the heating or cooling system.

When the single stage reciprocating compressor 10S is in a fully unloaded mode, i.e. all the suction cutoff unloader valve assemblies 14 are constantly on and, are therefore, not cycling in a pulse width modulated manner, the compressor 10S operates as described above until the point at which the compressed refrigerant is discharged from the cylinder 24L (or cylinders) into the plenum 40. Because all the suction cutoff unloader valve assemblies 14 are deactivated, the first portion of each of the suction cutoff unloader valve assemblies 14 is disposed to block discharge flow of the refrigerant from the plenum 40 to the piston portion of the suction cutoff unloader valve assembly 14. This configuration allows the biased piston portion of the suction cutoff unloader valve assembly 14 to move to a position where it substantially halts the flow of the refrigerant through the suction plenum 38 to the cylinder(s) 24L.

The controller 12 can be provided with control logic which allows a first suction cutoff unloader valve assembly 14 and a second suction cutoff unloader valve assembly 14 to alternate rapid cycling in a mode that allows one of the suction cutoff unloader valve assemblies 14 to operate in rapid cycling while the other suction cutoff unloader valve assembly 14 is not operated in rapid cycling but is disposed in the fully loaded position or the fully unloaded position. For example, the first suction cutoff unloader valve assembly 14 can operate in rapid cycling for a first time period. During the first time period, the second suction cutoff unloader valve assembly 14 is not operated in rapid cycling. At the end of the first time period the second suction cutoff unloader valve assembly 14 is then operated in rapid cycling for a second time period. During that second time period, the first suction cutoff unloader valve assembly 14 is not operated in rapid cycling. In this manner, the suction cutoff unloader valve assemblies 14 can be alternated in rapid cycling to achieve continuously variable part-load system capacity. Alternating the cycles of the valve assemblies can be achieved by the controller 12, which monitors and counts the number of rapid cycles for each valve and alternates the first and second suction cutoff unloader valve assemblies 14 based on the count to assure that the first suction cutoff unloader valve assembly 14 is not operated in a rapid cycling mode for a substantially higher number of cycles more than the second suction cutoff unloader valve assembly 14. In this manner, wear on any single valve assembly due to rapid cycling can be reduced. It is possible for a controller 12 to only count the number of cycles on one valve assembly 14 and when the number of cycles approaches a limit on this valve, the other valve would then be operated in the rapid cycling mode, while the first valve would stop operating in the rapid cycling mode. The counting does not need to be direct but, for example, can be estimated based on the number of days the compressor is in service or the number of hours the compressor has been operational, etc. In this case, for example, the switching between the valves can be done based on how many days one valve was operating in the rapid cycling mode versus the other valve. Alternating the cycling of the valves reduces the overall number of cycles each valve experiences to achieve the desired system part-load capacity. Thus, the service life of the suction cutoff unloader valves and reliability of the compressor can be increased via alternating the cycling of the valves.

One or more of the suction cutoff unloader valve assemblies 14 of the single stage compressor 10S can be operated in a pulse width modulation mode to provide a continuously variable capacity (part-load mode of operation) between the capacity achieved by the single stage compressor 10S when the suction cutoff unloader valve assemblies 14 are in the fully unloaded position, and the capacity achieved by the single stage compressor 10S when the suction cutoff unloader valve assemblies 14 are in the fully loaded position. The controller 12 can also be provided with control logic which allows rapid cycling of a first suction cutoff unloader valve assembly 14 and a second suction cutoff unloader valve assembly 14 to alternate in rapid cycling such that while one of the suction cutoff unloader valve assemblies 14 operates in rapid cycling the other suction cutoff unloader valve assembly 14 is not operated in rapid cycling but is disposed in the fully loaded position or fully unloaded position. The pattern, sequence, and number of suction cutoff unloader valve assemblies 14 alternated can be altered in the manner discussed above with reference to the multi-stage compressor 10M (FIG. 1A).

FIG. 2A is a partial sectional view of a portion of the compressor 10S or 10M with the suction cutoff unloader valve assembly 14 in a fully loaded position. FIG. 2B is a partial sectional view of a portion of the compressor 10S or 10M with the suction cutoff unloader valve assembly 14 in a fully unloaded position. In addition to the suction cutoff unloader valve assembly 14, lower stage cylinder head 16L, cylinder block 20, lower stage cylinder 24L, piston 26, and suction manifold 34, the compressor 10S or 10M includes a valve plate 44, fasteners 46, suction ports 48A and 48B, a suction valve 50, discharge ports 52A and 52B, a discharge valve 54, and a channel port 56. In addition to the suction plenum 38 and plenum 40, the cylinder head 16 includes a channel 58, guide walls 60, and a suction cutoff wall 62. The suction cutoff unloader valve assembly 14 includes the channel 58, channels 58A and 58B, a pressure chamber 64, a piston chamber 66, a valve piston 68, a valve 70, a solenoid 72, a valve body 74, and a bias spring 76.

In FIGS. 2A and 2B, the lower stage cylinder head 16L overlays the cylinder block 20 and the lower stage cylinder 24L. The valve plate 44 is disposed between the cylinder block 20 and the lower stage cylinder head 16L. The fasteners 46 secure the lower stage cylinder head 16L to the cylinder block 20. The valve plate 44 defines suction ports 48A and 48B. Suction port 48A extends through the valve plate 44 between the suction manifold 34 and the suction plenum 38. Suction port 48B extends through the valve plate 44 between the suction plenum 38 and the lower stage cylinder 24L. The suction valve 50 connects to the valve plate 44 and selectively covers the suction port 48B. The suction valve 50 is selectively movable from over the suction port 48B to allow refrigerant to enter the lower stage cylinder 24L. The discharge port 52A extends through the valve plate 44 between the lower stage cylinder 24L and the plenum 40. Discharge valve 54 connects to the valve plate 44 and interacts with the valve plate 44 to selectively cover and uncover the discharge port 52A. Discharge port 52B extends through the valve plate 44 between the plenum 40 and the intermediate or discharge manifold 36 or 42.

Channel port 56 extends through the lower stage cylinder head 16L to allow the channel 58 to communicate with the plenum 38. The channel 58 extends through the casing of the lower stage cylinder head 16L and stator casing portion of the suction cutoff unloader valve assembly 14. The guide walls 60 are internal walls in the lower stage cylinder head 16L which are sized to receive a movable portion of the suction cutoff unloader valve assembly 14. Similarly, the suction cutoff wall 62 is disposed adjacent the suction port 48A to extend into the suction plenum 38. The suction cutoff wall 62 interacts with another movable portion of the suction cutoff unloader valve assembly 14 to halt the flow of refrigerant through the suction plenum 38 to the lower stage cylinder 24L.

The channel 58 extends from the plenum 40 (through channel port 56) to the pressure chamber 64. The channel 58A extends from pressure chamber 64 through the stator portion of the suction cutoff valve assembly 14 to the suction plenum 38 (around the guide wall 60), while the channel 58B extends from the pressure chamber 64 through the stator portion of the suction cutoff valve assembly 14 to communicate with the piston chamber 66. The valve piston 68 is received between the guide walls 60 (which define the piston chamber 66) and is movable relative thereto. The valve 70 extends through the pressure chamber 64 and interconnects with the solenoid 72 which movably actuates the valve 70 within the pressure chamber 64. The valve 70 blocks channel 58 from fluid communication with the pressure chamber 64 when the suction cutoff valve assembly 14 enters the fully unloaded position. The valve 70 blocks channel 58A from fluid communication with the pressure chamber 64 when the suction cutoff valve assembly 14 enters the fully loaded position.

The piston chamber 66 receives the valve piston 68 therein. The valve piston 68 connects to the valve body 74 which extends through the suction plenum 38. The portion of the valve body 74 extending away from the valve piston 68 is configured to receive the bias spring 76. The bias spring 76 is disposed in the suction plenum 38 and contacts the valve body 74 and the wall of the low stage cylinder head 16L.

In FIGS. 2A and 2B, the suction port 48A provides a pathway for refrigerant to fluidly communicate from the suction manifold 34 to the suction plenum 38. Suction port 48B provides a pathway for refrigerant to be drawn by reciprocation of the piston 26 from the suction plenum 38 to the lower stage cylinder 24L. The suction valve 50 selectively covers the suction port 48B to substantially block fluid communication of the refrigerant from the suction plenum 38 to the lower stage cylinder 24L and is selectively movable from over the suction port 48B to allow refrigerant to enter the lower stage cylinder 24L during a suction portion of the piston 26 stroke. The discharge port 52A allows higher pressure compressed refrigerant to fluidly communicate from the lower stage cylinder 24L to the plenum 40 during the discharge stroke of the piston 26. The discharge valve(s) 54 selectively covers the discharge port(s) 52A to substantially block fluid communication of the refrigerant from the lower stage cylinder 24L to the plenum 40 until the refrigerant is a sufficient pressure to raise the discharge valve(s) 54 away from the valve plate 44. Discharge port 52B provides a pathway for compressed refrigerant to fluidly communicate from the plenum 40 to the intermediate or discharge manifold 36 or 42.

The channel 58 extends from the plenum 40 (through channel port 56) to the pressure chamber 64 to allow refrigerant to communicate therewith. In the fully loaded position illustrated in FIG. 2A, the channel 58A extending from the pressure chamber 64 to the suction plenum 38 is substantially blocked by the valve 70 which is actuated into this blocking position by the solenoid 72. Thus, the refrigerant is directed from the plenum 40 through the channel 58 to the pressure chamber 64, and from the pressure chamber 64 through channel 58B into the piston chamber 66. The compressed high pressure refrigerant causes the internal pressure to build within the piston chamber 66 to a level sufficient to overcome the bias on the valve body 74 by the bias spring 76. When overcoming this bias, the valve piston 68 and valve body 74 move within the piston chamber 66 and suction plenum 38 to a position which allows refrigerant to flow through the suction plenum 38 between the valve body 74 and the suction cutoff wall 62, such that the refrigerant can communicate with the low stage cylinder 24L through the suction port(s) 48B.

In the fully unloaded position illustrated in FIG. 2B, the solenoid 72 actuates the valve 70 away from a position which blocks communication of refrigerant through channel 58A. The actuation of the valve 70 moves the valve 70 to a position which blocks communication of refrigerant through channel 58. Thus, high pressure compressed refrigerant is substantially blocked from entering the piston chamber 66. The refrigerant in the piston chamber 66 is decreased in pressure by communication between the suction plenum 38 and piston chamber 66 (through channels 58A and 58B) and by a bleed orifice (not shown), which allows the refrigerant to bleed from the piston chamber 66 back into the channel 58.

By decreasing the pressure in the piston chamber 66, the pressure exerted on the valve piston 68 is insufficient to overcome the bias of the bias spring 76. The bias spring 76 moves the valve piston 68 and valve body 74 within the piston chamber 66 and suction plenum 38 to a position which substantially halts the flow of refrigerant through the suction plenum 38 between the valve body 74 and the suction cutoff wall 62. Thus, the configuration and arrangement of the valve body 74 and suction cutoff wall 62 do not allow for the flow of refrigerant to the lower stage cylinder 24L when the suction cutoff valve assembly 14 is in the fully unloaded position.

As discussed previously, the suction cutoff unloader valve assemblies 14 can be operated in a pulse width modulation mode to provide a continuously variable capacity (part-load mode of operation) between the capacity achieved by the compressor 10 (FIGS. 1A and 1B) when the suction cutoff unloader valve assembly 14 is in the fully unloaded mode, and the capacity achieved by the compressor 10S or 10M when the suction cutoff unloader valve assembly 14 is in the fully loaded position. More specifically, the solenoid 72 can be activated by the controller 12 (FIGS. 1A and 1B) to operate in a pulse width modulation mode and provide for a continuously variable capacity by moving the valve 70 to block and unblock the channels 58 and 58A in a rapid fashion to allow/disallow communication between the plenum 40 and the piston chamber 66 (and thereby cause valve piston 68 and valve body 74 to move relative to the suction cutoff wall 62 to block/unblock the flow of refrigerant through the suction plenum 38 to the lower stage cylinder 24L). The solenoid 70 can cycle between the fully loaded position of FIG. 2A, and the fully unloaded position of FIG. 2B, either rapidly or more slowly as dictated by the inertia of the system. In one embodiment, the cycle period of the suction cutoff unloader valve assembly 14 and solenoid 72 is between 0.3 second and 180 seconds. In another embodiment, the cycle period is between 3 seconds and 30 seconds. In yet another embodiment, the cycle period of the suction cutoff unloader valve assembly 14 is approximately 15 seconds.

Pulse width modulation of the solenoid 72 of the suction cutoff unloader valve assembly 14 allows for greater compressor 10 capacity control, thereby allowing the suction cutoff unloader valve assembly 14 to dial in on a desired compressor 10 capacity. Greater compressor 10 capacity control allows the refrigeration or air conditioning system to achieve improved temperature control accuracy, reliability, and energy efficiency.

As discussed previously, the controller 12 (FIGS. 1A and 1B) can also be provided with control logic which allows a first suction cutoff unloader valve assembly 14 and a second suction cutoff unloader valve assembly 14 to alternate cycling modes such that while one of the suction cutoff unloader valve assemblies 14 operates in the pulse width modulated mode the other suction cutoff unloader valve assembly 14 is not operated in the pulse width modulation mode but is disposed in the fully loaded position or the fully unloaded position. The pattern, sequence, and number of suction cutoff unloader valve assemblies 14 alternated can be altered in the manner discussed above with reference to the multi-stage compressor 10M (FIG. 1A).

FIG. 3A shows a portion of the suction cutoff unloader valve assembly 14 and lower stage cylinder head 16L in the fully loaded position. FIG. 3B shows the portion of the suction cutoff unloader valve assembly 14 and lower stage cylinder head 16L in the fully unloaded position. The low stage cylinder head 16L includes the suction plenum 38, the channel 58, and guide walls 60. In addition to the channel 58, the channels 58A and 58B, the pressure chamber 64, the piston chamber 66, the valve piston 68, the valve 70, and the solenoid 72, the suction cutoff unloader valve assembly 14 includes a movable bias member 78 and a bleed orifice 80.

Channel port 56 extends through the low stage cylinder head 16L to allow the channel 58 to communicate with the plenum 40. The channel 58 extends through the casing of the lower stage cylinder head 16L and stator casing portion of the suction cutoff unloader valve assembly 14. The guide walls 60 are internal walls in the low stage cylinder head 16L are sized to receive a movable portion of the suction cutoff unloader valve assembly 14. Similarly, the suction cutoff wall 62 is disposed adjacent suction port 48A to extend into the adjacent suction plenum 38. The suction cutoff wall 62 interacts with another movable portion of the suction cutoff unloader valve assembly 14 to halt the flow of refrigerant through the suction plenum 38 to the lower stage cylinder 24L.

The channel 58 extends from the plenum 40 (through channel port 56) to the pressure chamber 64. The channel 58A extends from pressure chamber 64 through the stator portion of the suction cutoff valve assembly 14 to the suction plenum 38 (around the guide wall 60), while the second channel 58B extends from the pressure chamber 64 through the stator portion of the suction cutoff valve assembly 14 to communicate with the piston chamber 66. The valve piston 68 is received between the guide walls 60 (which define the piston chamber 66) and is movable relative thereto. The valve 70 extends through the pressure chamber 64 and interconnects with the movable bias member 78 portion of solenoid 72 which actuates the valve 70 within the pressure chamber 64. The valve 70 blocks channel 58 from fluid communication with the pressure chamber 64 when the suction cutoff valve assembly 14 enters the fully unloaded position. The valve 70 blocks channel 58A from fluid communication with the pressure chamber 64 when the suction cutoff valve assembly 14 enters the fully loaded position. The bleed orifice 80 extends into the stator portion of the suction cutoff unloader valve assembly 14 and communicates with the channel 58.

The channel 58 extends from the plenum 40 (through channel port 56) to the pressure chamber 64 to allow refrigerant to communicate therewith. In the fully loaded position illustrated in FIG. 3A, the channel 58A extending from the pressure chamber 64 to the suction plenum 38 is substantially blocked by the valve 70 which is actuated into this blocking position by the solenoid 72. Thus, the refrigerant is directed from the plenum 40 through channel 58 to the pressure chamber 64, and from the pressure chamber 64 through channel 58B into the piston chamber 66. The compressed high pressure refrigerant causes the internal pressure to build within the piston chamber 66 to a level sufficient to overcome the bias on the valve body 74 by the bias spring 76 (FIG. 2A). When overcoming this bias, the valve piston 68 and valve body 74 moves within the piston chamber 66 and suction plenum 38 to a position which allows refrigerant to flow through the suction plenum 38 between the valve body 74 and the suction cutoff wall 62 such that the refrigerant can communicate with the low stage cylinder 24L through the suction port(s) 48B (FIG. 2A).

In the fully unloaded position illustrated in FIG. 3B, the solenoid 72 actuates the valve 70 away from a position which blocks communication of refrigerant through channel 58A. The actuation of the valve 70 moves the valve 70 to a position which blocks communication of refrigerant through channel 58. Thus, high pressure compressed refrigerant is substantially blocked from entering the piston chamber 66. The refrigerant in the piston chamber 66 is decreased in pressure by communication between the suction plenum 38 and piston chamber 66 (through channels 58A and 58B) and by a bleed orifice 80 which allows the refrigerant to bleed in one direction from the piston chamber 66 back into the channel 58.

By decreasing the pressure in the piston chamber 66, the pressure exerted on the valve piston 68 is insufficient to overcome the bias of the bias spring 76 (FIG. 2B). The bias spring 76 moves the valve piston 68 and valve body 74 within the piston chamber 66 and suction plenum 38 to a position which substantially halts the flow of refrigerant through the suction plenum 38 between the valve body 74 and the suction cutoff wall 62 (FIG. 2B). Thus, the configuration and arrangement of the valve body 74 and suction cutoff wall 62 do not allow for the flow of refrigerant to the lower stage cylinder 24L when the suction cutoff valve assembly 14 is in the fully unloaded position (FIG. 2B).

Although specifically described for the embodiments of the suction cutoff unloader valve assembly 14 and the compressors 10M and 10S illustrated, the manner of rapid cycling and/or alternating the cycling of the valves described herein is equally applicable to any compressor that utilizes valves designed to block and unblock one or more cylinders to alter the flow of refrigerant through the compressor. Additionally, the size of the cylinders may differ in other embodiments of the compressor. This invention applies to compressors operating with different types of refrigerant that can be used to heat, cool, and provide humidity control to a conditioned space. Some of the refrigerant types include, but not limited to R410A, R134a, R404A, CO2, and R22.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A reciprocating compressor, the compressor comprising: a first cylinder and a second cylinder; a first suction cutoff unloader valve integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the first cylinder; a second suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the second cylinder; and a controller configured to operate at least one of the first suction cutoff unloader valve assembly or second suction cutoff unloader valve assembly in the rapid cycling and monitor a number of rapid cycles for at least one suction cutoff valve.
 2. The reciprocating compressor of claim 1, wherein the compressor includes three or more suction cutoff unloader assemblies and wherein at least one of the suction cutoff unloader assemblies operates in the rapid cycling while at least one of the suction cutoff unloader assemblies does not operate in the rapid cycling.
 3. The reciprocating compressor of claim 1, wherein the rapid cycling includes an alternating cycling mode that operates the first suction cutoff unloader valve assembly in the rapid cycling, while the second suction cutoff unloader valve assembly is not operated in the rapid cycling but is disposed either in a fully unloaded position blocking the flow of refrigerant to the second cylinder or a fully loaded position allowing for uninterrupted flow of refrigerant to the second cylinder.
 4. The compressor of claim 3, wherein the controller operates the first suction cutoff unloader valve assembly in the rapid cycling for a first time period and the controller does not operate the second suction cutoff unloader valve in the rapid cycling during the first time period and then the controller operates the second suction cutoff unloader valve assembly in the rapid cycling for a second time period and does not operate the first suction cutoff unloader valve assembly in the rapid cycling during the second time period.
 5. The reciprocating compressor of claim 1, wherein the controller counts the number of cycles for each valve and alternates the first and second suction cutoff unloader valve based on the count to assure that the first suction cutoff unloader valve does not rapid cycle a substantial number of times more than the second suction cutoff unloader valve.
 6. The compressor of claim 1, wherein the first and second suction cutoff unloader valve assemblies have a cycle period of between 0.3 seconds and 180 seconds, when operated in the rapid cycling.
 7. The compressor of claim 1, further comprising a third cylinder and wherein the first cylinder is a lower stage cylinder and the second cylinder is a lower stage cylinder and the reciprocating compressor is a multi-stage compressor.
 8. The compressor of claim 7, wherein both the first suction cutoff unloader valve assembly and the second suction cutoff unloader valve assembly operate simultaneously in the rapid cycling.
 9. The compressor of claim 1, wherein rapid cycling is achieved through pulse width modulation of the first and second suction cutoff unloader valve assembly.
 10. A reciprocating compressor, the compressor comprising: a first cylinder and a second cylinder; a first suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the first cylinder; a second suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the second cylinder; and a controller configured to operate the first suction cutoff unloader valve assembly or second suction cutoff unloader valve assembly in rapid cycling as an alternating cycling mode which operates the first suction cutoff unloader valve assembly in the rapid cycling while the second suction cutoff unloader valve assembly is not operated in the rapid cycling.
 11. The compressor of claim 10, wherein the controller operates the first suction cutoff unloader valve assembly in the rapid cycling for a first time period and the controller does not operate the second suction cutoff unloader valve in the rapid cycling during the first time period and then the controller operates the second suction cutoff unloader valve assembly in the rapid cycling for a second time period and does not operate the first suction cutoff unloader valve assembly in the rapid cycling during the second time period.
 12. The reciprocating compressor of claim 10, wherein the controller counts the number of cycles for each valve and alternates the first and second suction cutoff unloader valve based on the count to assure that the first suction cutoff unloader valve does not rapid cycle a substantial number of times more than the second suction cutoff unloader valve.
 13. The compressor of claim 10, wherein the first and second suction cutoff unloader valve assembly have a cycle period of between 0.3 seconds and 180 seconds, when operated in rapid cycling.
 14. The compressor of claim 10, further comprising a third higher stage cylinder and wherein the first cylinder is a lower stage cylinder and the second cylinder is a lower stage cylinder and the reciprocating compressor is a multi-stage compressor.
 15. The compressor of claim 10, wherein rapid cycling is achieved through pulse width modulation of the first and second suction cutoff unloader valve assembly.
 16. A multi-stage reciprocating compressor, the compressor comprising: a lower stage cylinder and a higher stage cylinder, the higher stage arranged to receive refrigerant compressed in the lower stage cylinder; at least one suction cutoff unloader valve assembly integral with compressor and capable of rapid cycling to interrupt flow of refrigerant to the lower stage cylinder; and a controller configured to operate the at least one suction cutoff unloader valve assembly in the rapid cycling.
 17. The compressor of claim 15, wherein the at least one suction cutoff unloader valve assembly has a cycle period of between 0.3 second and 180 seconds, when operated in rapid cycling.
 18. The compressor of claim 15, wherein rapid cycling is achieved through pulse width modulation of the first suction cutoff unloader valve assembly.
 19. The multi-stage compressor of claim 15, further comprising: a second lower stage cylinder; and a second suction cutoff unloader valve assembly capable of rapid cycling to interrupt flow of refrigerant to the second lower stage cylinder.
 20. The multi-stage compressor of claim 18, wherein the controller operates both the first suction cutoff unloader valve assembly and the second suction cutoff unloader valve assembly simultaneously in rapid cycling. 